Portable electric tool motor construction



May 25, 1943.A G. c. wlLHlDE PORTABLE ELECTRIC TOOL MOTOR CONSTRUCTION Original Filed Feb. 18, 1941 Patented May 25, 1943 PORTABLE ELECTRIC TOOL MOTOR CONSTRUCTION Glenn C. Wilhidc, Baltimore County, Md., as-

signor to The Black and Decker Manufacturing Company, Towson, Md., a corporation of Maryland Original application February 18, 1941, Serial No. 379,413. Divided and this application October 7, 1941, Serial No. 414,032

9 Claims.

This application is a division of application Serial No. 379,413, led February 18, 1941.

The invention relates to the construction of portable electric tools and particularly to the motor housing or i'leld casing and stator and the manner of mounting and securing the stator to overcome existing defects and causes of failure. The motors of these tools, due to the limitations imposed by the conditions incident to the use of the tools, both for portability and for convenience in operating in conned spaces, must be as small, compact and light as the power, speed, rigidity and durability requirements will permit. In motors of the threephase type and other motors made to meet these conditions there is insuicient room for screws and similar fastening means passing through the laminations of the stator iron or eld core in the direction of the motor axis, which is a usual construction in motors for other purposes where a lesser degree of compactness is required.

On account of this diiiculty, it has been customary in the construction of small portable electric tool motors of this type to fasten the stator iron or iield core by means of set screws extending through the motor casing and threaded into the stator iron. Such screws have been radially disposed and located at Various points.

The tools are ordinarily operated with the chuck and bit and gear casing disposed downwardly and there is a constant tendency for any of the motor parts which may be in any way released to drop down into the ian with consequent injury to the fan or to the winding. In y these constructions if the fastenings are suiciently loosened the stator tends to slip down and come into contact with the ian with the result that the windings are damaged and the motor requires major repairs in the nature of replacement of the windings.

The form herein disclosed is adapted to use in tools where an integral eld casing or housing is considered a necessity or an advantage. In this instance, the casing cr field housing has contacting surfaces or lands arranged about its inner circumference and preferably spaced to provide for ventilation and adapted to engage the peripheral surface of the stator, and the casing is contracted circumfercntially by transverse tension members causing these contacting surfaces to grip the stator which is thus clamped and held stationary. It may be held against longitudinal motion by the transverse members shown in the form of bolts which apply the contracting tension or by other suitable means. In the form shown the casing has a yielding or compressible area extending longitudinally and spanned by the tension means whereby the casing is contracted to clamp the stator or lield, and prevent shifting and rotation thereof.

In the accompanying drawing, I have illustrated a portable electric tool embodying the features of my invention in the preferred form.

In the drawing:

Figure l is a side elevation of an electric drill, equipped with a motor embodying the features of my invention in the preferred form, the central portion of the ligure being broken away to show the motor and casing in section on a vertical plane of the axis of the motor, the handle being broken away for convenience of illustration.

Fig. 2 is a section on the line 2 2 in Fig. l, looking in the direction of the arrows. y

The construction shown is particularly adapted for use in a portable or hand supported and directed tool where an integral rigid casing is desired. In this form of motor the casing is so constructed that it may be contracted by transverse screw bolts or pinch bolts and the casing has inwardly projecting portions extending longitudinally on its inner surface which contact the stator core or laminations when the casing is thus contracted, clamping the stator in position and in the preferred construction the stator has transverse grooves engaged by the screw bolts or pinch bolts or other suitable means and providing a positive positioning of the stator in the direction of the axis, and otherwise, whereby even in the event of the loosening of the pinch bolts there is no harmful yielding or displacement of the stator either in the direction of the axis or in a circumferential direction.

More specifically described, the construction shown comprises a motor or field casing 40 at the opposite ends of which are shown the usual gear casing 4i and hand grip 32 respectively. These may be secured in any suitable manner as by means of bolts i3 and 44 or other suitable securing means, preferably outside the casing.

In the construction shown, the bolts 43 are passed through lugs 65 on the gear casing and lugs on the eid casing or housing and the bolts 44 are passed through lugs 4l, d8, all of which lugs are suitably located and bored in alignment and the standard construction includes a gear cover plate 49.

The motor 50 enclosed in the motor housing or iield casing 4U has a shaft 5| on which is mounted a cooling fan 52 and the stationary eld or stator indicated by vreference character 53 consists of stator iron or core 64 and coil 55 and the rotor is indicated by reference character 56.

While the construction may be regarded as particularly adapted for use in portable tools equipped with the three phase or high frequency motors with which the high power tools of small size and extreme compactness are most generally equipped, it is `adapted for use in similaritools with universal and other types of motor, particularly where small overall dimension relative to power output is desirable or essential.

In accordance with the preferred construction the eld casing or housing 40 is provided with projections 57, having lands, otherwise defined as clamping areas or surfaces 58, arranged on a circumference or bore which corresponds rather closely to the circumference of the stator iron or clore 54, being normally, i. e., in the absence of the contraction to be described, adapted to admit the stator with reasonable freedom. The clamping surfaces or areas 58 separately or collectively may be of sufficient longitudinal extent to contact the outer `peripheral surfaces 39 of the core 55 supporting the laminations throughout substantially the entire length of the stator core 54 the bore being such that surfaces 58 on projections 5? are adapted to clamp and position the core when the eld casing or housing is contracted as above suggested. The grooves 59, or passages, between the projections I assist in cooling and Ventilating the motor, otherwise continuity of surfaces 5S would be feasible.

The eld casing or housing it as already pointed out, is preferably of the unitary type, i. e., in a single piece cr similarly constructed. This housing is provided with a compressible area preferably located at the bottom of the casing, as the tool is held normally in horizontal position, so that it is toward the operator and `out of the way under the usual circumstances of operation. This is shown in the form of a box or channel section 50 projecting downwardly away from the motor shaft 5l as seen in both Figs. 1 and 2 and extending longitudinally of the field casing or housing and parallel to the axis or substantialiy so. Any suitable compressible element may be substituted for said box section 50.

In the form shown there is a cavity or groove El enclosed by said channel and the walls of said channel are suiciently thin to provide the desired degree cf compressibility. It may be noted that. in, the form shown, which, as pointed out, is subject to a wide range of substitution and variation, the bottom wall 52 of the channel is of a thi 'mess having a reducing taper toward the transverse center 63.

In the form shown, this box section or channel 6i! is spanned by pinch bolts or through bolts 55 in suitable holes 55 formed in bosses E6.

In the form shown, these bolts pass through transverse grooves 5l in the stator core 5i neair its opposite ends whereby the stator is secured against displacement particularly in the direction of its axis but also against rotation. In this capacity bolts di have a keying function, other means being usabie for this purpose within the broad scope of the invention contemplated.

It is of particular importance that as the bolts 54 are tightened the box section 5t tends to yield, it being found that .in the absence of the stator the transverse diameter of the housing as at iii can be contracted to the extent of approximately ooo to im@ of an inch.

CTL

Assuming that the lands or clamp-ing surfaces 58 of the projections 51 are arranged on a bore or in a cylindrical or other suitable surface of dimensions suicient to admit the stator core 54 allowing for a play of 1/1000 or W100() of an inch, and the bolts 64 are then tightened, the lands or clamping surfaces 5S will grip the stator tightly preventing it from rotating in the housing, the tension being normally suiiicient to also prevent longitudinal motion of the stator.

In combination with this gripping means, the pinch bolts 6d in the grooves 57 eliminate any possibility in the case of relaxation of the tension of these bolts, that the stator or field 53 may yield in an axial direction downwardly or toward the fan bringing the coil 55 into contact therewith. It is also notable that there are no movable or removable nuts or bolts or other fastenings inside the casing which may become loosened or released and by entering the fan or contacting the rotating parts cause injury to the motor.

I have thus described specifically and in detail the application of the principles of my invention and the manner of constructing, applying, operating and using the same, the description being specific and in detail in order that the manner of constructing, operating and using the invention may be fully understood, however, the specific terms herein are used descriptiveiy rather than in a limiting sense, the scope of the invention being defined in the claims. t

What I claim as new and desire te secure by Letters Patent is:

l. A portable electric tool having a held casing adapted to support at its opposite ends, a gear casing and a handle, said tool having in said field casing a motor with a stator and a stator coro, the eld casing having inwardly projecting'portions with their inner surfaces arranged in correspondence with the circumference of the core and means for contracting the circumference of the field casing whereby' said surfaces grip and ciamp the core.

2. A portable electric tool having a field casing adapted for attachment of a gear casing at one end and a handle at the other end, said tool having a motor in said eld casing with a stator and stator core, said field casing being of exible construction and adapted to circumferential contraction and having means for engaging the circumference of the core and transversely extending means for contracting the casing to clamp the core,v the core having transverse surfaces engaging the latter means to prevent longitudinal motion of the core.

3. A portable electric tool having a field casing with a motor therein, the motor having a stator with a stator core, said casing having inwardly projecting portions with clamping surfaces thereon spaced about its inner periphery and the surfaces being arranged in close conformanceto the circumference of the core, said casing being, i

adapted for circumferential contraction and having transverse tension means spaced outwardly from the axis for contracting the casing to grip the core, said projecting portions being spaced apart to provide Ventilating passages.

4. A portable electric tool having a field casing with a motor therein, the motor having a stator with a stator core, said casing having inwardly projecting portions with clamping surfaces thereon spaced about its inner periphery, the surfaces being 'arranged in close conformance to the circumference of the core but adapted to admit the core, said casing being adapted for circumferential contraction and having transverse tension means spaced outwardly from the axis for contracting the core, the core having transverse surfaces engaging said transverse means whereby the core is held against motion in the direction of its axis.

5. A portable electric tool having a iield casing with a motor therein, the motor having a stator' with a stator core, said casing having inwardly projecting portions with clamping surfaces thereon spaced about its inner periphery and the surfaces being arranged in close conformance to the outer longitudinal surface of the core, said casing being adapted for circumferential contraction A and having transverse tension means for contracting the casing to grip the core, the said inwardly projecting portions on the inner periphery of the casing being in the form of longitudinal ribs providing longitudinal Ventilating passages between the ribs.

6. A portable electric tool having a field casing and a motor therein, the motor having a stator with a laminated core, the field casing having inwardly disposed surfaces arranged in the form of a bore of a size slightly exceeding the size of the core and conforming to its surface, said casing having a longitudinally extending channel portion and transverse bolts for contracting said channel portion and thereby contracting the casing to grip the core.

7. A portable electric tool having a neld casing and a motor therein, the motor having a stator with a laminated core, the eld casing having inwardly disposed surfaces arranged in a bore, exceeding the diameter of the core and conforming to its surface, said casing having a longitudinally extending channel portion and transverse bolts for contracting said channel portion and also contracting the casing to grip the core, said core having transverse surfaces to prevent longitudinal motion of said core, by engagement with said transverse bolts.

8. An electric tool having a field casing with a motor therein, the motor having a stator with a core, the eld casing having an opening of a diameter slightly exceeding the diameter of the core, the casing being adapted to be circumferentially contracted and means for contracting the casing to cause the latter to grip the core, said contracting means comprising bolts arranged transversely to the axis, the core being apertured to admit and engage the bolts, thus positioning the core in the direction of its axis.

9. An electric tool having a eld casing with a motor therein, the motor having a stator with a core, the eld casing having an opening of a diameter slightly exceeding the diameter of the core, the casing being adapted to be circumferentially contracted and means for contracting the casing to cause the latter to grip the core, the core and contracting means having mutually contacting surfaces transverse to the motor axis to locate the core and to prevent longitudinal displacement of the core.

GLENN C. WILIrHDE. 

